Metal filament.



UNITED STATES PATENT orro,

WILLIAM D. COOLIDGE, 0F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEXV YORK.

METAL FILAMENT.

N 0 Drawing.

To all whom it may concern Be it known that I, TILL-TAM D. CooniDoE, a citizen of the United States, residing at Schenectady, in the county of Schenectady and State of New York, have invented certain new and useful Improve ments in Metal Filaments, of which the following is a specification.

I have developeda process for making filaments of refractory material such as tungsten, molybdenum, titanium, boron, and other refractory powders of various kinds, by utilizing as a binding material for the powder, a ductile alloy having such characteristics that it can be impregnated with the powder and then extruded through a die to shape the mixture into wires. After wires have thus been formed consisting of a con glomerate mixture of metal binder and refractory powder, I heat them in suitable manner to drive out the binder and to shrink and sinter the refractory residue into firm coherent conductors suitable for use as lamp filaments.

According to my present invention, I add to a conglomerate mixture of the type above mentioned, a diluting compound of such a nature that on heating it will react with one of the metallic components of the mixture to form a porous material and a pure metal. The latter serves asa binder for the other components until driven out at higher heat treatments, While the porous material serves to soak up the liquid constituents during the early stages of the heat treatment, thereby preventing the formation of globules of fused metal along the wire under treatment and otherwise assisting in 'the production of a uniform refractory conductor or filament.

The components of this diluting compound are eventually driven from the filament with the result that the finished filament is of considerably less diameter than the original wire. This feature is of importance as tending to cheapen production and as rendering easythe manufacture of lamp filaments of exceedingly small cross-section.

Although my process is a general one, I will proceed by describing one embodiment employed by 'me with success.

Powdered tungsten and powdered cuprio oxid are rubbed into a warm and plastic amalgam consisting 0144 parts cadmium to .44: parts mercury to 12 parts bismuth. The

Specification of Letters Patent.

tu e heated wit;

Patented Tile-y lei, 11912,

Application filed September 23, 1908. Serial No. 454,446.

mixture of tungsten and oxid is addul to [he amalgam to the extent of per cent. it this mixture the relative proportiom l)x= tween tungsten and oxid mav \arv through wide limits, as from a very small pr V tage of oxid'to parts oxid and i tungsten, according to the amount ots' age desired, the amount of metal hinder produced from the compound, and amount of porous mat" al i king li uid constituents of the .01 found desirable in any particuhir case. The conglomerate mass thus produ ed consists of the cadmium-bismuth. amalgam :w' e as a binder and the powdered tung .-n and cupric oxid held in place by the binder. This mixture is next squirted warm tin-(nigh a diamond die andcomes out as a sil\ erwhite ductile wire. This vv're is cut into suitable lengths and then ha in an etacuated a gas flame to a temperature at which the mercury and possibly some of the :"aahuimu dis il from the wire. This heat treatment also produces another important change in the wire, namely, that of cruising chemical reaction between the cad: u of he amalgam and the cupric oxid .ed as a diluent, thereby producing metal ic copper and cadmium onid. This reaction goes on very easily and smoothly and the temperature need not greatly exceed 300 degrees C.

\Ylieu the filaments come from the baking operation they consist of tungsten powder and cadmium oXid held together by a binder of bismuth, CGPPOI, and pos ibly some cadmium. The amount of the latter component depends, of course, on the proportion of cupric oxid added to the mixture, for if a small quantity. only is added then more cadmium will remain behind unoxidized. In the next step, the filaments are heated in a vacuum to higher illlll .'llltlll', to produce vaporization of the cadmium and of the hismuth, and finally, vaporization of the copper and direct distillation of the cadmium oxid. inasmuch as the cadmium oXid comes off last it is present when the cadmium and bismuth change over from the solid to the liquid state and can therefore operate to soak up the liquid metal and keep it from running together into globules during that interval of time before the temperature is high enough to produce complete vapori zation. After the binding material and the diluent are all out of the filament, the temperature may be still further increased to sinter and shrink the tungsten and render it more stable and otherwise better suited for use in an incandescent lamp. This heat treatment may be effected by current passed directly through the filament or in any other suitable manner. Inasmuch as the process is operative with high percentage of diluent, it is altogether possible to produce a finished tungsten filament having a diameter much less than that of the die through which the original plastic mass was squirted.

According to the procedure above described, the removal of the'vaporizable components is elt'ected in a vacuum. If desired, an atmosphere of hydrogen may be used during this treatmentin which case the cadmium and bismuth come out as before butthe cadmium oxid is reduced by the hydrogen and leaves the filament Pll01 to vaporization of the copper.

As a typical embodiment of my invention, I have disclosed the use of cupric oxid. This is a good material for this purpose as it can be obtained in fine and pure condition by simply oxidizing in air the very fine copper carbonates now on the market as pigments. Furthermore, the cupric oXid will react with the cadmium within the comparatively small temperature range between the removal of the mercury and the removal of the cadmium by baking. And in addition, the copper liberated from the oxid does not in any way contaminate the tungsten or impair its refractory qualities. I do not, however, wish to be limited as to the scope of this process, except by the appended claims.

hat I claim as new and desire to secure by Letters Patent of the United States, is,

1. The method which consists in producing a ductile mixture containing a metallic binder, a finely divided refractory material, and a diluent capable of combining with one component of the binder, forming a body of desired. shape therefrom, etfecting chemical reaction between said diluent and said binder and then removing from said mixture all components except said highly refractory material.

2. The method which consists in forming wires containing a metallic binder, a highly refractory powder and a chemical compound, heating to cause reaction between said compound and one componentof said binder, and subsequently heating to a higher temperature to drive from the wire all com-.

ponents except said highly refractory material.

3. The method which consists in producing a wire containing a cadmium alloy, tungsten and cupric oxid, heating to effect oxidation of at least part of said cadmium,

and subsequently heating to a higher temperature to successively drive out allcasily vaporizable comporwnts.

4. The method which consists in forming a wire containing a metallic. bindrr, a finely divided refractory material and a chemical compound capable of reacting with one component of said binder to produce a relatively stable material, heating to effect this chemi- -cal reaction and then heating to higher temperatures to remove from the wire all components except said highly refractory material.

5. A ductile wire consisting of a refractory powder, a chemical compound and a metallic binder, said compound being such that it will react chemically with one component of said binder to form a relatively stable material.

6. A wire consisting of a cadmium alloy, a refractory powder and a compound capable of reacting with cadmium to produce. a porous and relatively stable material.

7. A wire consisting of a cadmium amalgam, cupric oxid, and a finely divided refractory material.

A wire containing cadmium, bismuth, mercury, tungsten and cupric. oxid.

9. The method which consists in heating a wire containing refractory material, metallic binder, and suitable metal compound to cause chemical reaction between said compound-and at least a portion of said binder and eliminate all substances except said refractory material and produce a filamentary body containing only said refractory material and to produce by said reaction a relatively stable porous compound of an element of said binder.

10. The method which consists in forming a body of desired shape containing refractory material, metallic binder, and compound of metal having a higher point of fusion than said binder, heating to cause chemical reaction between said compound and said binder and by said reaction producing a relatively stable porous compound of anelement of said binder and liberation of said higher melting metal, and to eliminateall substances except said refractory material.

11. The process of treating a filamentary; body containing refractory material and binding material plastic at relatively low temperature and additional material which consists in heating said body to effect removal of said binding material and to cause" the additional material to become effective 'as a coherent metallic binder of fusion temperature approximating the temperature at which heat tends to consolidate the refractory material, and then heating to a. higher temperature to remove said additional material and to produce a coherent body containing only said refractory material.

12. A wire containing refractory material,

.a mixture containing' refrzn'tory mareria low melting metal binder. and compound of higher melting metal. Sflltl eomponnrl being capable of reacting with saicl binder with resulting liberation of eaitl higher melt ing metal.

13. An unfinished filamentary body comprising refractory material, low-melting: metal bintler, and higher melting metal capable 0E remaining in Said hotly at a tenn pe attire ninler which said ref 'a '.'tory n'iaterial tenrls to consolidate.

ll. The process which consists in forming a filamentary borly containing material ini tially eli'ecting as himler nml metallic compound, anrl treating such body to cause the liberation from such compound of metal which awn; as binrler for maintaining the filamentary hotly in a coherent condition nntil it begins to possess coherenee imlepentlently of any binder anti eonrert it into a filament coneisliing wholly of refractory material.

1-3. The process which ('UllnlSlS in forming antl material initially en' 'tive as hinilerani other material. *hapingr Silitl miIi'lnre as (lt' slre h antl treatin the shaped holly to ran- 2 snch other ma in the lilifillllt: in become an eli'ecti're bintl r to lJOtlY in a eol'ierent eonoirnm nntil the maintain the fractory nniterial itself begins to r-ohere am convert it into one consisting Wholly of re fraetory material.

16. The inetho l of converting a filamentary botly containing material initially ell'eelive as binder and other material i to a eoherent refractory hotly Whion eonsi Q in lirnt heating to remove the material iniiially effective as binder antl to cause such other material to become an cli' eclive binder for maintaining the filamentary hotly in a eoherent condition for subsequent treatment aml then heating to a higher temperature to eliminate everything except a retractory residue from the filament and consolidate sneh re:-'itlne.

1?. A mixture for the production of ret'raemry bodies: comprising material. which is initially ellectire as binder to allow shaping of the mixture and other material which becomes an effective binder tlnring the process of converting the shapetl hotly into a 1 coherent retraetory one and serve: to maintain the hotly in a coherent etmoition ilnring 7 each [)l'ifl jtii witness whereof. I have hereunto llb' llnt (lay of September; 190%.

Kl LLlli H l). EL YUOL'Z QUE. 

